Needs per-domain persistence, not global

You can control with shortcuts, but buttons such as + and-are not displayed.
Do I need to do anything?

it's great and super helpful! but could you add a reset button? i sometimes speed up during advertisements and then i have to click multiple times to get it back to 1x

edit: ok, pressing "r" resets..... i just usually use the actual controls, and there was no button for it. you might want to consider adding it!

The controls not always show up on the video. How to make the controls to show up?

A absolutely must have extension. Unfortunately it is not updated and cause malfunction on some pages like this one
https://www.ellinikahoaxes.gr/
(thumbnails of videos do not load)
IMO that should be a build in firefox feature not an extension.
That alone, that this extension is no longer updated, is reason enough for me to consider switching to chrome.

Works great, does exactly what I wanted it to, except for one thing:

When the add-on is enabled, I can't play two videos at the same time (say, I have two YouTube tabs open for, say, a podcast with no background music and background music). I don't know why; I don't know if that's a bug or a feature, but if it's a feature, it's a bad one, and I'd at least like to see an option to disable that.

If it is a bug, please fix it. I'm adding it as an issue on your GitHub.

Keep up the good work, though. Again, I gave this a 4/5 for a reason.

5 star if you can make 4x speed tickable

I tried this extension on Firefox for Android. It only works for a few common websites like YouTube. For the other websites, it doesn't work - the controller is clickable. Meanwhile, the extension for PC works well for all websites.

Very good, works as advertised. It's just that even with a modern 6-core 4.5Ghz CPU and 32GB of RAM, the sound quality in speed-up is really bad (much worse than Enounce Myspeed or many Chrome extensions doing video speed up).

If the author would improve the sound quality (give a selection for low-cpu-impact/bad quality and higher-cpu-demand/super-quality audio algo), then it would be perfect 5 stars.